Conventionally, an electrical junction box (which is also called a power distributor) for distributing power from a power source (battery) to loads such as headlights and windshield wipers is mounted in an automobile. The electrical junction box includes a busbar that is connected to the power source and is part of a power circuit, and a circuit board including a control circuit for controlling the flow of electric current in the power circuit. The control circuit includes a circuit pattern formed on the circuit board, and electronic components such as switching elements (e.g., relays and FETs (field effect transistors)) and control elements (e.g., microcomputers and control ICs (integrated circuits).
In recent years, in order to reduce the size of the electrical junction box, circuit assemblies in which a circuit board is arranged integrally with the top of a busbar have been developed. As an example, JP 2005-117719A discloses a circuit assembly manufactured by using an adhesive sheet to bond the busbar and the circuit board together. In some cases, the control circuit provided on the circuit board needs to be electrically connected directly to the busbar in the circuit assembly as shown in JP 2005-224053A. JP 2005-224053A proposes a connection method in which a connection chip is used as an intermediary. Specifically, JP 2005-224053A discloses a circuit assembly in which a conductive pad is provided on one side of the circuit board, a through hole through which the busbar is exposed is formed at a position adjacent to the conductive pad. A connection chip having a shape spanning the through hole and the conductive pad is soldered to both the busbar and the conductive pad. In the circuit assembly disclosed in JP 2005-224053A, the busbar and the conductive pad are electrically connected to each other via the connection chip.